Synergetic use of altimetry and surface drifters to increase resolution and accuracy of sea level anomaly and geostrophic current maps in the Gulf of Mexico

Sandrine Mulet (CLS, France)

CoAuthors

Hélène Etienne (CLS, France); Maxime Ballarotta (CLS, France); Yannice Faugere (CLS, France); Gérald Dibarboure (CNES, France); Nicolas Picot (CNES, France)

Event: 2019 Ocean Surface Topography Science Team Meeting

Session: Science III: Mesoscale and sub-mesoscale oceanography

Presentation type: Type Oral

Strong improvements have been made in our knowledge of the surface ocean geostrophic circulation thanks to satellite observations. However, the synergy of different sources of observation (satellites and in-situ) is mandatory in order to go toward higher resolution. In this study, we combined altimetric along track Sea Level Anomalies (SLA) with geostrophic velocity estimated from surface drifters in order to map SLA and associated geostrophic current anomalies in the Gulf of Mexico.

First, an important work is done to pre-process drifter data to extract the geostrophic component of the signal in order to be consistent with physical content of altimetry. This step includes estimate and remove of Ekman current, Stokes drift and wind slippage. Two kind of drifters are used:
- Drifters from Woods Hole Group Company (this company, part of CLS group, launches their own drifter in the Gulf of Mexico for their downstream services).
- The drifters launched in the framework of the Lagrangian Submesoscale ExpeRiment(LASER) campaign (January-April 2016).

Second, drifters and along track SLA from Jason2, HY2, Saral and Cryosat-2 are combined through multivariate objective analysis to map a daily time series of SLA and associated geostrophic current anomalies from 01/09/2015 to 30/04/2016.

Finally, comparisons with independent data show the better agreement of maps merging both altimetry and drifters especially for the meridional component of geostrophic current. A spectral analysis underlines also the improvement.

 

Oral presentation show times:

Room Start Date End Date
The Forum Wed, Oct 23 2019,17:30 Wed, Oct 23 2019,17:45
Sandrine Mulet
CLS
France
smulet@groupcls.com